Lithium metal has many uses and, to name a few, they include nuclear power application where a blanket of the liquid metal or its molten salts is used for breeding purposes in nuclear fusion reactors, in lightweight, compact lighium/sulfur batteries for electric cars and for power plant load leveling purposes, as a degasifier in the production of high-conductivity copper and bronze, and in the synthesis of compounds for use in the field of medicine.
Lithium metal is generally produced by electrolysis of an eutectic mixture of highly pure molten lithium chloride and potassium chloride.
There are naturally occurring brines in the United States which contain reasonable concentrations of lithium, in the form of the chloride, so as to be considered viable reserves for lithium recovery. Three particular sources include Searle's Lake, Calif., the Great Salt Lake, Utah, and Clayton Valley, Nev. The latter is the most economical source of lithium since the magnesium to lithium ratio is low, generally about 1.15:1, which allows for a simplified process of concentrating, purifying and recovering lithium chloride brine. Lithium carbonate is then obtained by treatment of the brine with soda ash.
To make lithium metal, the lithium carbonate is converted to lithium hydroxide via a liming process, and the latter compound in turn is converted to lithium chloride by treatment with hydrochloric acid followed by drying. This is a very circuitous and expensive route to lithium chloride, since lithium originally exists as the chloride in the natural brine. Thus, for many years there has been the need for a direct economical method for recovering lithium chloride as such from natural brines.
It is a primary object of the present invention to provide an economical method based on the use of solar energy for concentrating lithium chloride brines to a degree not heretofore obtained, including those brines which occur in nature.
Another object of this invention is to employ solar energy in such a way that brines of relatively low lithium chloride content may be concentrated to brines saturated with respect to such compound.
Still another object of this invention is to provide an integral step in an overall process for the economic recovery of high purity lithium chloride directly from naturally occurring brines.